diff --git a/index.h b/index.h
index d54a5ca..134962e 100644
--- a/index.h
+++ b/index.h
@@ -6,16 +6,18 @@
 #include <iostream>
 #include <utility>
 #include <vector>
+#include <variant>
 #include <map>
 
 
 namespace usql {
 
+using IndexValue=std::variant<long, std::string>;
 using rowid_t = size_t;   // int is now enough but size_t is correct
 
 static const int k_default_rowids_size = 16;
 
-template<typename K>
+
 class Index {
 public:
 	Index(std::string index_name, std::string col_name, ColumnType type) :
@@ -25,7 +27,7 @@ public:
 			throw Exception("creating index on unsupported type");
 	}
 
-	void insert(K key, rowid_t rowid) {
+	void insert(IndexValue key, rowid_t rowid) {
 		auto search = m_index.find(key);
 		if (search != m_index.end()) {
 			if (m_uniq)
@@ -40,7 +42,7 @@ public:
 		}
 	}
 
-	void remove(K key, rowid_t rowid) {
+	void remove(IndexValue key, rowid_t rowid) {
 		auto search = m_index.find(key);
 		if (search != m_index.end()) {
 			search->second.erase(find(search->second.begin(), search->second.end(), rowid));
@@ -49,7 +51,7 @@ public:
 		}
 	}
 
-	std::vector<rowid_t> search(K key) {
+	std::vector<rowid_t> search(IndexValue key) {
 		auto search = m_index.find(key);
 		if (search != m_index.end()) {
 			return search->second;
@@ -74,8 +76,8 @@ public:
 
 //	void dump() {
 //		std::for_each(m_index.begin(), m_index.end(),
-//			      [](std::pair<K, std::vector<rowid_t>> element){
-//			K key = element.first;
+//			      [](std::pair<IndexValue, std::vector<rowid_t>> element){
+//			IndexValue key = element.first;
 //			std::vector<rowid_t> rowids = element.second;
 //			std::cout << "key: " << key << ",  rowids count:" << rowids.size() << std::endl;
 //		});
@@ -99,7 +101,7 @@ private:
 	std::string		m_column_name;
 	ColumnType		m_data_type;
 
-	std::map<K, std::vector<rowid_t> > m_index;
+	std::map<IndexValue, std::vector<rowid_t> > m_index;
 };
 
 }	// namespace
\ No newline at end of file
diff --git a/table.cpp b/table.cpp
index 45586d0..a8cae48 100644
--- a/table.cpp
+++ b/table.cpp
@@ -263,13 +263,13 @@ void Table::validate_row(Row &row) {
 	row.set_visible();
 }
 
-void Table::create_index(const Index<IndexValue>& index) {
+void Table::create_index(const Index& index) {
 	m_indexes.push_back(index);
 }
 
 bool Table::drop_index(const std::string &index_name) {
 	auto it = std::find_if(m_indexes.begin(), m_indexes.end(),
-						   [&index_name](const Index<IndexValue> &idx) {
+						   [&index_name](const Index &idx) {
 							   return idx.get_index_name() == index_name;
 						   });
 
@@ -281,7 +281,7 @@ bool Table::drop_index(const std::string &index_name) {
 }
 
 
-void Table::index_row(Index<IndexValue> &index, const ColDefNode &col_def, const Row &row, const size_t rowid) {
+void Table::index_row(Index &index, const ColDefNode &col_def, const Row &row, const size_t rowid) {
 	if (col_def.type==ColumnType::integer_type) {
 		index.insert(row[col_def.order].getIntValue(), rowid);
 	} else if (col_def.type==ColumnType::varchar_type) {
@@ -291,7 +291,7 @@ void Table::index_row(Index<IndexValue> &index, const ColDefNode &col_def, const
 	}
 }
 
-void Table::unindex_row(Index<IndexValue> &index, const ColDefNode &col_def, const Row &row, const size_t rowid) {
+void Table::unindex_row(Index &index, const ColDefNode &col_def, const Row &row, const size_t rowid) {
 	if (col_def.type==ColumnType::integer_type) {
 		index.remove(row[col_def.order].getIntValue(), rowid);
 	} else if (col_def.type==ColumnType::varchar_type) {
@@ -301,7 +301,7 @@ void Table::unindex_row(Index<IndexValue> &index, const ColDefNode &col_def, con
 	}
 }
 
-void Table::reindex_row(Index<IndexValue> &index, const ColDefNode &col_def, const Row &old_row, const Row &new_row, size_t rowid) {
+void Table::reindex_row(Index &index, const ColDefNode &col_def, const Row &old_row, const Row &new_row, size_t rowid) {
 	unindex_row(index, col_def, old_row, rowid);
 	index_row(index, col_def, new_row, rowid);
 }
@@ -350,18 +350,18 @@ void Table::index_rows(const std::string &index_name) {
 }
 
 
-Index<IndexValue> * Table::get_index(const std::string &index_name) {
+Index * Table::get_index(const std::string &index_name) {
 	auto it = std::find_if(m_indexes.begin(), m_indexes.end(),
-						   [&index_name](const Index<IndexValue> &idx) {
+						   [&index_name](const Index &idx) {
 							   return idx.get_index_name() == index_name;
 						   });
 
 	return (it != m_indexes.end()) ? &(*it) : nullptr;
 }
 
-Index<IndexValue> * Table::get_index_for_column(const std::string &col_name) {
+Index * Table::get_index_for_column(const std::string &col_name) {
 	auto it = std::find_if(m_indexes.begin(), m_indexes.end(),
-							[&col_name](const Index<IndexValue> &idx) {
+							[&col_name](const Index &idx) {
 								return idx.get_column_name() == col_name;
 							});
 
diff --git a/table.h b/table.h
index 45f17e0..730277f 100644
--- a/table.h
+++ b/table.h
@@ -43,22 +43,22 @@ struct Table {
 
 	void print();
 
-	std::string m_name;
+	std::string				m_name;
 	std::vector<ColDefNode> m_col_defs;
-	std::vector<Row> m_rows;
-	std::vector<Index<IndexValue>> m_indexes;
+	std::vector<Row>		m_rows;
+	std::vector<Index>		m_indexes;
 
 	static long string_to_long(const std::string &s);
 	static double string_to_double(const std::string &s);
 
 	void create_row_from_vector(const std::vector<ColDefNode> &colDefs, const std::vector<std::string> &csv_line);
 
-	void create_index(const Index<IndexValue>& index);
+	void create_index(const Index& index);
 	bool drop_index(const std::string &index_name);
 
-	static void index_row(Index<IndexValue> &index, const ColDefNode &col_def, const Row &row, size_t rowid);
-	static void unindex_row(Index<IndexValue> &index, const ColDefNode &col_def, const Row &row, size_t rowid);
-	static void reindex_row(Index<IndexValue> &index, const ColDefNode &col_def, const Row &old_row, const Row &new_row, size_t rowid);
+	static void index_row(Index &index, const ColDefNode &col_def, const Row &row, size_t rowid);
+	static void unindex_row(Index &index, const ColDefNode &col_def, const Row &row, size_t rowid);
+	static void reindex_row(Index &index, const ColDefNode &col_def, const Row &old_row, const Row &new_row, size_t rowid);
 
 	void index_row(const Row &row);
 	void unindex_row(const Row &row);
@@ -66,8 +66,8 @@ struct Table {
 
 	void index_rows(const std::string &index_name);
 
-	Index<IndexValue> * get_index(const std::string &index_name);
-	Index<IndexValue> * get_index_for_column(const std::string &col_name);
+	Index * get_index(const std::string &index_name);
+	Index * get_index_for_column(const std::string &col_name);
 
 
 	struct rows_scanner {
diff --git a/usql_dml.cpp b/usql_dml.cpp
index c8d060d..9102f49 100644
--- a/usql_dml.cpp
+++ b/usql_dml.cpp
@@ -29,7 +29,7 @@ std::pair<bool, std::vector<rowid_t>> USql::look_for_usable_index(const Node *wh
 				) {
 					auto col_name = ((DatabaseValueNode *)ron->left.get())->col_name;
 
-					Index<IndexValue> * used_index = table->get_index_for_column(col_name);
+					Index * used_index = table->get_index_for_column(col_name);
 					if (used_index != nullptr) {
 						std::vector<rowid_t> rowids = used_index->search((ValueNode *)ron->right.get());
 #ifndef NDEBUG